1. Field of the Invention
This invention relates to photographic cameras, and more particularly to a light metering system which provides either of a through-the-lens light metering mode and an outside-the-lens light metering mode.
2. Description of the Prior Art
The through-the-lens (TTL) light metering aspect of a photographic camera is of importance in the point of determining the correct exposure, as the light value sensing element is arranged to receive light passing through the objective lens of the camera, thereby the angular field picked up by the lens and the light-permeability of the lens can be taken into account to perform the light metering with high accuracy over the entire area of the view field. However, in many dark rooms and at night photography applications, the decreased amount of light impinging upon the light value sensing element by the objective lens and half-mirror makes it more difficult to perform the light metering and accordingly exposure control with high accuracy particularly when the light level falls outside the linear dynamic range of the light value sensing element. The camera with TTL light metering has a drawback of limiting the exposure control accuracy to a considerable extent in the low light level exposure range.
In order to eliminate such a drawback, it has been realized in some of cine cameras to combine the TTL light metering system with an outside-the-lens (OTL) light metering system where an additional light value sensing element is employed as arranged to receive light coming from an object being photographed directly without passing through the objective lens. For example, in making exposures for objects in dark rooms or at night, the light value sensing element adapted for use in the OTL light metering mode and which is normally shielded from the light as movably mounted in the camera housing is brought out therefrom. With such an OTL light metering system, however, the angular field actually picked up by the objective lens is not inherently taken into account in determining the exposure value. Since the fidelity of the OTL light metering system is very low, its use is limited to particular photography applications such as with bulb exposure (indefinite timed exposure).